Sensor and detection system having wide diverging beam optics

ABSTRACT

A sensor and detection system is included. The sensor includes at least one transmitter which has associated optical elements for emitting at least one light beam toward the object to be detected. At least one receiver is positioned adjacent the transmitter for receiving light reflected from an edge of the object. The receiver generates a signal responsive to the reflected light. The associated optical elements of the transmitter include a converging lens for emitting a focused light beam in one plane, and a cylindrical lens for emitting a diverging light beam in another plane, such that a portion of the reflected light is diverging and is received by the receiver over a wide angle of coverage.

FIELD OF THE INVENTION

The present invention relates generally to a sensor and detection systemfor detecting the presence or position of surfaces, and moreparticularly to a sensor and detection system having wide diverging beamoptics for increasing the angle of detection coverage.

BACKGROUND OF THE INVENTION

Sensors are used for a variety of purposes. One useful purpose is as andetection system for detecting the presence of objects. In particular ithas been found to be difficult to detect the edge of objects, or objectswith small, specular surfaces. A sensor and detection system and methodwhich solves this problem is taught in U.S. Pat. No. 5,504,345, which isowned by assignee, and is herein incorporated by reference. The '345patent discloses a semiconductor wafer and magnetic disk edge detectionsystem having converging dual-beam optical sensor. The sensor comprisesat least two light sources, and at least two light detectors. The lightsources, or the light beams emanating form the sources, are spatiallyoriented such that the focal point of the converging light beams definea focal or inspection plane and converge at a single point external tothe sensor. When the object interrupts the beam at or near the focalpoint of the light sources, it causes the light to be reflectedbackwards toward the sensor by the light detectors. The light detectorsare spatially arranged so they can receive the light reflected.

The '345 patent teaches a very useful device, however it would be usefulto increase the angle of coverage of the sensor. When the light strikesthe object and is reflected backwards there is a certain angleassociated with the return path of the reflected light. It is possiblefor light to be reflected in a vicinity remote from the light detectors.This results in a "blind spot" where the light is not detected. Thus, itis desirable to provide a sensor and detection system that exhibitsimproved coverage and substantially eliminates blind spots.

OBJECTS AND SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide asensor and detection system with improved angle of coverage.

More specifically, it is an object of the present invention to provide asensor and detection system having wide diverging beam optics.

Another object of the present invention is to provide a sensor anddetection system capable of detecting the edge of objects, particularlyobjects having small, specular or reflective surfaces.

Still another object of the present invention is to provide a sensor anddetection system capable of detecting the edge of an object where theedge is at an angle of incidence that deviates significantly from theposition which would generate ideal reflection to the receiver.

These and other objects, features and advantages of the invention areachieved by the sensor and detection system of the present invention,comprising at least one transmitter having associated optical elementsfor emitting at least one light beam toward the object to be detected.At least one receiver is positioned adjacent the transmitter forreceiving light reflected from an edge of said object when said objectintersects the one light beam. The receiver generates a signalresponsive to the reflected light. The associated optical elements ofthe transmitter include a converging lens for emitting a focused lightbeam in one plane, and a cylindrical lens for emitting a diverging lightbeam in a perpendicular plane, such that a portion of the reflectedlight is diverging and is received by the receiver over a wide angle ofcoverage.

In an alternative embodiment of the present invention, a detectionsystem is provided which comprises the sensor as described above, andincludes means for causing relative movement between the object and theat least one transmitter, and a position encoder for providing proximityand location data responsive to the signal, thereby detecting theobject.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention become apparent upon reading of the detailed description ofthe invention provided below and upon reference to the drawings, inwhich:

FIG. 1 is a partially cut away top plan view of the sensor according toone embodiment of the present invention.

FIG. 2 is a schematic diagram showing the light beam and optics of thepresent invention in greater detail.

FIG. 3 is a schematic diagram of the sensor showing the case of idealreflection back to the receiver.

FIG. 4 is a side view of the sensor of the present invention.

FIG. 5 is a perspective side view of an object to be detected by thesensor of the present invention showing the light striking the surfaceof the object in the x and y planes.

FIG. 6 is a partially cut away top plan view of the sensor according toa second embodiment of the present invention and shows how the sensor ofthe present invention may detect an object that is present at an angleof incidence that deviates significantly from position which wouldgenerate ideal reflection to the receiver.

FIG. 7 is a diagram of an detection system in accordance with thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Turning to the drawings, wherein like components are designated by likereference numerals, FIGS. 1 and 2 are two views of the sensor anddetection system of the present invention. FIG. 1 shows a sensor 5comprising a housing 10 and wherein the housing 10 contains at least onetransmitter 12 and at least one receiver 14. The transmitter 12 andreceiver 14 are spaced apart from each other, and are mounted on aprinted circuit board (not shown) within the sensor housing 10.

The transmitter 12 emits light 16 which is directed towards the object18 to be detected. The light is reflected off the object 18 back towardsthe receiver 14.

The receiver 14 is a light detector and is spaced apart from thetransmitter for receiving the reflected light 17. It is important tonote that a plurality of receivers and transmitters may be used,however, the present invention is also capable of increasing the rangeof accurate detection and measurement using just one transmitter andreceiver pair. Also, the placement of the transmitters and receivers mayvary. For example, two transmitters may be placed directly next to oneanother, with the receivers placed on the other side of each of thetransmitters. Alternatively, the transmitter and receiver may be placedin alternating position (such as one receiver, one transmitter, onereceiver, and so on). In the preferred embodiment the sensor comprisesthree receivers and two transmitters, in alternating position.

Of particular advantage, the sensor employs a special opticalarrangement that provides for detection of objects over a greater angleof coverage. That is, the sensor is capable of detecting objects thathave a highly curved or specular surface, and/or are present at an anglethat deviates significantly from the position which would generate idealreflection to the receiver. The case of direct, or ideal, reflection isshown in FIG. 3. In FIG. 3, the maximum possible amount of the reflectedlight received is being receiver by the receiver 14. The opticalarrangement of the present invention is shown in more detail withreference to FIG. 2. The transmitter 12 includes a light source andassociated optics. The light source 20 emits a light beam 21.Preferably, the light source 20 is a laser having a laser driver circuitand at least one laser (both not shown). The light 21 emitted from thelight source 20 is projected onto a converging lens 22. The converginglens 22 focuses the light. Of particular advantage, after the lightpasses through the converging lens 22, the light is directed to acylindrical lens 24. According to the present invention, the cylindricallens is a diverging lens which diverts the light only in one plane. Forpurposes of description, we shall define this plane as the "horizontal,"or x-axis plane. For instances where the objects to be detected areintended to lie within parallel planes, this horizontal plane isparallel to said parallel planes. In the perpendicular plane, i.e. the"vertical" or y axis plane, the light is unaffected and not diverted,and remains focused. Thus, the light that exits the transmitter isdiverging in one plane, and focused in another (or perpendicular) plane.Preferably, the cylindrical lens is a negative plano-cylindrical lens.

The diverging light in the horizontal plane provides a wide angle ofcoverage. That is, when light strikes the object, it is reflectedbackwards toward the sensor. If the light reflects back in the area of areceiver, the light will be detected by the receiver and then detectionand position measurements occur. However, if the object is highlyspecular and/or curved, or is present at an angle, the light beingreflected back toward the sensor may be in an area away from thereceiver, and thus the reflected light is not detected. To increase therange of detection by the receiver, the diverging light beam is employedby the present invention. Since the beam is diverted in one plane, awider light beam strikes the object and this causes a wider beam ofreflected light back to the sensor. In other words, in the one plane,i.e. the horizontal plane, or the plane that is parallel to the object,the light is diverted so that when the light strikes the object, even ifthe object is at an angle, some portion of the light will be received atthe receiver. This prevents the potential problem that light reflectingback may miss the receiver. This wider beam of reflected light increasesthe range that the reflected light will be detected by one of thereceivers 14. The reflected light will be reflected back toward thereceivers at the same angle as the incoming, or incident light.

In the vertical, or y axis plane, the light from the transmitter 12 isfocused and is spatially oriented such that the focused beam from thelight source converges to a single focal point, external to the sensor 5(note this is not shown in the top view). This focal point defines aninspection plane. When the object 18 to be detected interrupts the beamat or near the focal point of the light source, it causes the light tobe reflected backwards towards the sensor for detection by the receiver14. The receiver 14 generates a signal from the received light byconventional digital signal processing techniques, and this signal isthen used to determine detection of the object, its location and thelike. Thus, it is shown that the present invention provides a sensor anddetection system wherein at one plane or axis, there is a diverging beamwhich provides for the receiver to "see" the object over a wide angle;while in the other plane or axis the beam is focused which promotesprecise detection of the object.

FIG. 4 shows a side view of the sensor wherein the light is focused. Asillustrated, in this plane or axis, the beam is focused for precisedetection of the object. The advantage of providing diverging light andfocused light is further illustrated in FIG. 5. FIG. 5 shows an object18 having a curved or specular surface, such as a semiconductor wafer.Light is emitted from the sensor 5 toward the object 18. In thisinstance where the surface of the object is collinear to the centerlineof the light beam, the light is reflected directly back to the sensor 5.However, the present invention is also capable of detecting lightreflected from the curved edges of the object. The wide diverging lightemitted from the sensor is diverted in the x-axis, and as shown, strikesthe object at various points along the object's curved surface whichlies in the plane of the x-axis. The light is then reflected backtowards the sensor's receivers thereby providing a wide angle ofcoverage. The angle of coverage is considered wide as compared to theangle of the reflected light that is reflected from a focused beam. Now,looking at the vertical plane (i.e. the perpendicular or y-axis) thesensor provides for a focused light beam in this plane. This promotesvery accurate detection by the sensor. For example, to detect thelocation of the top and bottom surfaces of the object 18, the sensor andfocused beam can be moved in the vertical plane to locate the top andbottom surfaces. Thus, while the light in the horizontal plane isdiverted giving a wide angle of coverage, the light is focused in thevertical plane thereby providing accurate detection.

FIG. 6 shows an alternative embodiment of the invention employing aplurality of transmitters and receivers. Preferably, the sensorcomprises two transmitters 12 and three receivers 14, in alternatingpositions for extending the coverage of the sensor. When two or moretransmitters are used, each transmitter emits a focused light beam inthe vertical plane, and these converging light beams are spaced apartsuch that the focal point of the converging light beams define a focalor inspection plane and converge as a single point external to thesensor. Relative motion of the object and sensor occurs, and then theobject to be detected interrupts the beam at or near the focal point ofthe two light sources, it causes the light to be reflected backwardstowards the sensor for detection by the receivers. As shown, the lightwill be reflected back at an angle φ1 that is the same angle as that ofthe incoming or incident light. As stated above, the receivers 14 thengenerate signals responsive to the reflected light, and these signalsare then processed to provide detection and location data.

In an alternative embodiment of the invention, a detection system isprovided. Referring to FIG. 7, an example of the detection system isillustrated. The detection system includes a sensor 5 which ispreferably mounted on a movable arm 30, such as a motor arm, or arobotic arm. The sensor 5 is directed toward objects 18 to be detectedand/or located, and may be moved from one end of the objects to theother by the movable arm 30. The objects 18 may be mounted in a tray 33and placed on moving means 34, such as a transfer table or conveyor.Operatively coupled to the sensor is an encoding means 32, such as anoptical encoder and the like. The encoding means 32 receives a signalfrom the sensor 5 and generates the desired data. The encoding means 32may employ various encoding algorithms known in the art to determineposition and/or location of the object 18. A transporter 36, such as arobotic arm, may also be mounted to the movable arm for transportingobjects 18 to and from the carrier 33.

Thus, an improved sensor and detection system has been provided. Theforegoing description of specific embodiments of the invention have beenpresented for the purpose of illustration and description. They are notintended to be exhaustive or to limit the invention to the precise formsdisclosed, and obviously many modifications, embodiments, and variationsare possible in light of the above teaching. It is intended that thescope of the invention be defined by the claims appended hereto andtheir equivalents.

What is claimed:
 1. A sensor for detecting an edge of a substantiallyflat object, the sensor comprising:at least one transmitter for emittingat least one respective light beam toward the edge of said substantiallyflat object to be detected; and at least one receiver for receivinglight reflected from the edge of said substantially flat object whensaid object intersects the at least one light beam, and for generating asignal responsive to the light reflected from the edge of saidsubstantially flat object; wherein the at least one transmitter isconstructed to emit a converging, focused light beam in a first planefor precise detection of said object, said focused light beam being adiverging light beam in a second plane, such that a portion of thereflected light is diverging and is received by the receiver over a wideangle of coverage; wherein said first plane is disposed at an angle tosaid second plane.
 2. The sensor of claim 1 wherein the at least onetransmitter comprises a converging lens and a cylindrical lens.
 3. Thesensor of claim 2 wherein the cylindrical lens is a negative planocylindrical lens.
 4. The sensor of claim 1 wherein the signal isprocessed by digital signal processing.
 5. The sensor of claim 1 whereinsaid sensor comprises two transmitters and three receivers, thetransmitters being spaced apart and with one of said receivers locatedon each side of the transmitters, wherein the receivers receive lightemitted from either of the transmitters that is reflected from theobject.
 6. The sensor of claim 1 wherein the sensor is for detectingmultiple objects lying within parallel planes.
 7. The sensor of claim 1wherein the object is present at an angle that deviates significantlyfrom a position which would generate ideal reflection to the receiver.8. The sensor of claim 1 further comprising:means for causing relativemovement between the object and the at least one transmitter; andposition encoding means for providing proximity and location dataresponsive to said signal.
 9. The sensor of claim 8 wherein the meansfor causing relative movement between the object and the at least onetransmitter is selected from the group of a motor arm, robotic arm,conveyor belt, transfer table, a disk indexing system, by hand, andcombinations thereof.
 10. The sensor of claim 1, wherein said firstplane is disposed at a substantially perpendicular angle to said secondplane.
 11. The sensor of claim 1, wherein said diverging light beam isan undivided light beam.
 12. The sensor of claim 1, wherein saidsubstantially flat object is substantially parallel to said secondplane.
 13. The sensor of claim 1, wherein the at least one transmittercomprises a first lens constructed to emit the focused light beam in thefirst plane, and a second lens constructed to emit the diverging lightbeam in the second plane.
 14. The sensor of claim 1, wherein saidconverging, focused light beam converges to a focal plane.
 15. Thesensor of claim 14, wherein the focal plane is substantiallyperpendicular to the first plane and the second plane.
 16. The sensor ofclaim 1, wherein said converging, focused light beam converges along itsentire extent in the first plane.
 17. A detection system for detectingan edge of a substantially flat object, the detection systemcomprising:at least one transmitter having associated optical elementsfor emitting at least one respective light beam toward the edge of saidsubstantially flat object to be detected; moving means for causingrelative movement between the object and the at least one transmitter;at least one receiver for receiving light reflected from the edge ofsaid substantially flat object when said object intersects the at leastone light beam, and for generating a signal corresponding to the lightreflected from the edge of said substantially flat object; and aposition encoder for providing position information of the objectresponsive to the signal; wherein the associated optical elementsinclude means for emitting a converging, focused light beam in a firstplane for precise detection of said object, said focused light beambeing a diverging light beam in a second plane perpendicular to thefirst plane, such that a portion of the reflected light is diverging insaid second plane and is received by the receiver over a wide angle ofcoverage in said second plane.
 18. The detection system of claim 17wherein the means for emitting comprises a converging lens and acylindrical lens.
 19. The detection system of claim 18 wherein thecylindrical lens is a negative plano-cylindrical lens.
 20. The detectionsystem of claim 17 wherein the signal is processed by digital signalprocessing, in cooperation with position encoding means to provideinformation of the object's proximity and location.
 21. The detectionsystem of claim 17 wherein said sensor comprises two-transmitters andthree receivers, the transmitters being spaced apart and with one ofsaid receivers located on each side of the transmitters, wherein thereceivers receive light emitted from either of the transmitters that isreflected from the object.
 22. The detection system of claim 17 whereinthe detection system is for detecting multiple objects lying withinparallel planes.
 23. The detection system of claim 17 wherein the objectis present at an angle that deviates significantly from a position whichwould generate ideal reflection to the receiver.
 24. The detectionsystem of claim 17 wherein the moving means is selected from the groupof a motor arm, robotic arm, conveyor belt, transfer table, a diskindexing system, by hand, and combinations thereof.
 25. The detectionsystem of claim 17, wherein said diverging light beam is an undividedlight beam.
 26. The detection system of claim 17, wherein saidconverging, focused light beam converges to a focal plane.
 27. Thedetection system of claim 26, wherein the focal plane is substantiallyperpendicular to the first plane and the second plane.
 28. The detectionsystem of claim 17, wherein said converging, focused light beamconverges along its entire extent in the first plane.
 29. A detectionsystem for detecting an edge of a substantially flat object, thedetection system comprising:at least one transmitter having associatedoptical elements for emitting at least one respective light beam towardthe edge of said substantially flat object to be detected, said at leastone respective light beam being diverging in one optical axis whichdefines an inspection plane, and said at least one light beam being aconverging focused light beam in a second optical axis, the beam in saidsecond optical axis being focused to a predetermined point along saidsecond optical axis; moving means for causing relative movement betweenthe object and the at least one transmitter; at least one receiver forreceiving light reflected from the edge of said substantially flatobject when said object intersects the inspection plane, and forgenerating a signal corresponding to the received light; and a positionencoder for providing position information of the object responsive tothe signal; wherein said at least one light beam strikes the edge ofsaid substantially flat object in said one optical axis such that aportion of the reflected light is diverging and is received by thereceiver over a wide angle of coverage; further wherein said at leastone light beam strikes the edge of said substantially flat object insaid second optical axis for precise detection of said object.
 30. Thedetection system of claim 29, wherein said at least one light beam is anundivided light beam.
 31. The detection system of claim 29, wherein saidconverging, focused light beam converges to a focal plane.
 32. Thedetection system of claim 31, wherein the focal plane is substantiallyperpendicular to said one optical axis and said second optical axis. 33.The detection system of claim 29, wherein said converging, focused lightbeam converges along its entire extent in the second optical axis.